title: Factor inhibiting HIF (FIH-1) promotes renal cancer cell survival by protecting cells from HIF-1α-mediated apoptosis.
abstract: BACKGROUND
  Clear cell renal cell carcinoma (CCRCC) is the commonest form of kidney cancer. Up to 91% have biallelic inactivation of VHL, resulting in stabilisation of HIF-α subunits. Factor inhibiting HIF-1 is an enzyme that hydroxylates HIF-α subunits and prevents recruitment of the co-activator CBP/P300. An important question is whether FIH-1 controls HIF activity in CCRCC.
  
  
  METHODS
  Human VHL defective CCRCC lines RCC10, RCC4 and 786-O were used to determine the role of FIH-1 in modulating HIF activity, using small interfering RNA knockdown, retroviral gene expression, quantitative RT-PCR, western blot analysis, Annexin V and propidium iodide labelling.
  
  
  RESULTS
  Although it was previously suggested that FIH-1 is suppressed in CCRCC, we found that FIH-1 mRNA and protein are actually present at similar levels in CCRCC and normal kidney. The FIH-1 inhibition or knockdown in the VHL defective CCRCC lines RCC10 and RCC4 (which express both HIF-1α and HIF-2α) resulted in increased expression of HIF target genes. In the 786-O CCRCC cell line, which expresses only HIF-2α, FIH-1 attenuation showed no significant effect on expression of these genes; introduction of HIF-1α resulted in sensitivity of HIF targets to FIH-1 knockdown. In RCC4 and RCC10, knockdown of FIH-1 increased apoptosis. Suppressing HIF-1α expression in RCC10 prevented FIH-1 knockdown from increasing apoptosis.
  
  
  CONCLUSIONS
  Our results support a unifying model in which HIF-1α has a tumour suppressor action in CCRCC, held in check by FIH-1. Inhibiting FIH-1 in CCRCC could be used to bias the HIF response towards HIF-1α and decrease tumour cell viability.
authors.affiliation: Centre for Cell Signalling and Molecular Genetics, Rayne Institute, University College London, London, WC1E 6JF, UK.
authors.forename: M N
authors.initials: MN
authors.lastname: Khan
authors.forename: T
authors.initials: T
authors.lastname: Bhattacharyya
authors.forename: P
authors.initials: P
authors.lastname: Andrikopoulos
authors.forename: M A
authors.initials: MA
authors.lastname: Esteban
authors.forename: R
authors.initials: R
authors.lastname: Barod
authors.forename: T
authors.initials: T
authors.lastname: Connor
authors.forename: M
authors.initials: M
authors.lastname: Ashcroft
authors.forename: P H
authors.initials: PH
authors.lastname: Maxwell
authors.forename: S
authors.initials: S
authors.lastname: Kiriakidis
mesh_terms: D000600:Amino Acids, Dicarboxylic / Q000494:pharmacology; D017209:Apoptosis; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology; D045744:Cell Line, Tumor; D002470:Cell Survival; D019610:Cytoprotection; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology*; D007680:Kidney Neoplasms / Q000473:pathology*; D006899:Mixed Function Oxygenases; D012097:Repressor Proteins / Q000502:physiology; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000502:physiology; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D000600:Amino Acids, Dicarboxylic; D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D006899:Mixed Function Oxygenases; D012097:Repressor Proteins; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C439790:HIF1AN protein, human; C497446:VHL protein, human; C040947:oxalylglycine